The primary goal of this K08 Award is to prepare Dr. Matthew McHugh for a career as an independent investigator devoted to outcomes research at the health policy environment level. Specifically, the Award will provide the candidate with the opportunity to: 1) engage in intensive study and training focused on the statistical methods and analytic techniques required to empirically evaluate the effect of health policies and regulations on quality of care-.sensitive patient outcomes, and 2) conduct a health policy outcomes study under the mentorship of Linda Aiken, PhD, FAAN, RN, Jeffrey Silber, MD, PhD, and Mark Pauly, PhD. The specific aims of this study are to: 1) determine the effect of California's minimum nurse-to-patient staffing ratio legislation on risk-adjusted acute myocardial infarction (AMI) mortality and the influence of hospital occupancy rates or overcrowding, hospital market structure, and demographic characteristics such as income level and race on this effect, and 2) determine the effects of nurse staffing, hospital occupancy rates, and hospital market structure on AMI mortality and relationship among those variables. The hypotheses that will be tested are: 1) AMI mortality will be lower in CA compared to a control state, Pennsylvania after the implementation of the staffing law. This effect will be reduced for patients admitted at periods of high occupancy. The effect will be amplified in areas of higher hospital competition and the effect will be reduced for low-income persons as well as racial minorities, and 2) Better nurse staffing, lower occupancy rates, and higher levels of competition will be associated with lower AMI mortality. The effect of nurse staffing on mortality will be moderated by occupancy rate and hospital competition. The specific aims will be accomplished through an observational study using a multiple time series design with a difference-in-differences approach, using PA as a control state. Within-year regression analyses will also be performed to understand the relationships between the variables and outcomes of interest. Using discharge abstract-based administrative data will allow determinations of occupancy and occupancy rates that match with the day each individual patient is admitted. The proposed study will help determine the impact of California legislation (and similar laws being considered in more than 25 other states) mandating minimum nurse-to-patient ratios in hospitals. The study examines health outcomes for patients admitted with heart attacks - one of the most common reasons for hospitalization. It examines how legislated nurse-to-patient ratios, nurse staffing levels, and hospital overcrowding may affect patient outcomes.